The present invention relates to a new process for preparing cis-chrysanthemic acid comprising hydrolysis of trans-.delta.-halogenodihydrochrysanthemic acid or ester thereof (Step I), conversion of trans-.delta.-hydroxydihydrochrysanthemic acid ester to cis-chrysanthemic acid and iso-cis-chrysanthemic acid (Step II), and separation of cis-chrysanthemic acid from the mixture by selective conversion of iso-cis-chrysanthemic acid to cis-dihydrochrysanthemolactone.